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Re: [Xen-devel] [RFC] Correct/fast timestamping in apps under Xen [1 of
| To: | Jeremy Fitzhardinge <jeremy@xxxxxxxx>, Dan Magenheimer <dan.magenheimer@xxxxxxxxxx> |
|---|---|
| Subject: | Re: [Xen-devel] [RFC] Correct/fast timestamping in apps under Xen [1 of 4]: Reliable TSC |
| From: | Keir Fraser <keir.fraser@xxxxxxxxxxxxx> |
| Date: | Sat, 10 Oct 2009 07:35:24 +0100 |
| Cc: | Tim Deegan <Tim.Deegan@xxxxxxxxxxxxx>, "kurt.hackel@xxxxxxxxxx" <kurt.hackel@xxxxxxxxxx>, Ian Pratt <Ian.Pratt@xxxxxxxxxxxxx>, "Xen-Devel \(E-mail\)" <xen-devel@xxxxxxxxxxxxxxxxxxx> |
| Delivery-date: | Fri, 09 Oct 2009 23:35:49 -0700 |
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| Thread-index: | AcpJbjtY3cPWX4bcSE+M7fSvzBNdxQABZ1nh |
| Thread-topic: | [Xen-devel] [RFC] Correct/fast timestamping in apps under Xen [1 of 4]: Reliable TSC |
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On 10/10/2009 06:55, "Jeremy Fitzhardinge" <jeremy@xxxxxxxx> wrote: > The kernel does about between 400k and 1.4M/sec, median around ~600k, > for a git pull (which I think is single-threaded), and about > 200k-500k/sec for a kernel compile (-j4 on 2 vcpus). Usermode is a much > lower rate; around 1000/sec for the kernel compile. > > Baseline idle is around 1000/sec kernel, 10/sec user. > > Also, my inline naked rdtsc benchmark shows that the emulated rdtsc is > taking around 465ns (vs 30, a 15x slowdown). Hmmm... So at 600k/sec, the kernel spends an appreciable amount of time (1-2%) doing RDTSCs? And with emulation that'll be more like 25-30%. It's quite a surprisingly high rate. -- Keir _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxxxxxxxx http://lists.xensource.com/xen-devel |
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